Resistive-capacitive (RC) active filters are of considerable interest to integrated circuit designers. An RC-active realization of a high-pass notch filter utilizing a differential amplifier and only two capacitors is described in "A Single Operational Amplifier Biquadratic Filter Section" by J. J. Friend, 1970 IEEE Int.Symp.Circuit Theory (Atlanta, Ga., Dec. 14, 1974) pp. 179-180. However, filters of this type cannot attain a gain higher than unity. The main drawback in the sensitivity of most such canonical notch realizations is that their pole frequencies depend upon the d-c amplifier gain, A.sub.o.